The present invention relates to apparatus for controlling gas delivery to a patient. The apparatus of the present invention is related to apparatus disclosed in applicant""s copending PCT application AU96/00679 filed Oct. 31, 1996 and in AU Patent 632932 entitled xe2x80x9cAnalysis System for physiological variablesxe2x80x9d, the disclosures of which are incorporated herein by cross reference.
The apparatus of the present invention may provide a diagnostic and/or a therapeutic function. The diagnostic function may include monitoring and/or diagnosis of physiological variables associated with the patient. The therapeutic function may include application of controlled gas delivery to the patient. The diagnostic and therapeutic functions may be performed in a single device having integrated functions or it may be performed via two or more separate devices.
The apparatus of the present invention is particularly useful for investigation, diagnosis and treatment of sleep, respiratory and sleep related respiratory disorders, sleep propensity, fatigue and asthma and will be described herein in that context. Nevertheless it is to be appreciated that it is not thereby limited to such applications.
The apparatus of the present invention has been developed for, but is not limited to monitoring, analysing, storing, controlling and networking physiological variables. The aforementioned xe2x80x9ccontrolling of physiological variablesxe2x80x9d includes controlling the gas delivery to a patient. This gas can be but is not limited to air as used in a CPAP (Continuous Positive Air Pressure) application, or one of the many variations of positive air pressure delivery to a patient known in the art.
Due to the complex and varying states of sleep and the broad range of sleep disorders that can be diagnosed, many different physiological variables and events can be simultaneously monitored, analysed and stored by the present apparatus. The monitored physiological variables and events can include one or more channels of each of the following signal types:
Status of lights
Graphic processing of video image (allows determination of whether patients eyes are open or closed).
Patient digital video recording and graphic processing techniques for determination of eye lid activity (ie status of patient eyes being opened or closedxe2x80x94relative to fully closed or fully opened eyes status).
Time and date stamping of monitored physiological data, video and sound.
Infrared Video monitoring (for night studies)
Complex sound analysis (accurate full bandwidth or limited bandwidth recording and analysis of breathing sounds. The sound is analysed and compared with criteria or a data base, consisting of reference data for disordered breathing. Microphones may be servo controlled for automatic axis adjustment to allow optimum focus on breathing sounds.)
Physiological events: ie ECG arrhythmia, EEG spike detection, EEG spindles amongst others
Local area networked monitoring, analysis and/or storage of a patient""s physiological variables
Endoscopy
Breath by breath analysis-pnuemotachograph
3D imaging
Virtual patient monitoring
Infrared eye detection for fatigue and sleep monitoring
EEG delta and alpha-wave detection
Eye position and movements by way of Infrared Eye Detection
Delta Wave detections and related sleep/fatigue/impairment detection
Mattress Device: monitoring of patient sleep state and respiratory parameters by using a mattress sensor device. The matress device can be used to monitor a patient""s electro-oculogram, sleep state; arousals, position, electrocardiogram. There are presently two types commercially available mattress devices; Static Charge-sensitive Bed (SCSB) and polyvinylidene fluoride (PVDFxe2x80x94piezoelectric plastic).
When monitoring sleep states, sleep propensity, respiratory disorders, vigilance state or fatigue of a subject, one or more physiological variables as listed above may be continuously monitored and/or analysed and/or stored.
The present invention allows one or more channels of patient variables and/or events to be monitored, processed and recorded, while at the same time allowing precise data interconnection with a remote site. This remote site can view, process or record the real-time patient data. The communication link can take the form of a range of transmission media, including but not limited to wireless interconnection such as spread spectrum transmission wireless LAN.
The prior art provides devices for the purpose a patient""s breathing but these devices are unable to apply principles of acoustic cancellation as proposed by the present invention. While the applicant appreciates the prior systems can monitor patient breathing sound and in particular snoring, these earlier devices were not developed to modulate gas delivery to a patient in a way which can acoustically cancel vibration in the patient""s upper palate.
According to the present invention there is provided apparatus for controlling gas delivery to a patient""s, said delivery being indented to maintain effective respiratory function, said apparatus including:
a monitoring component adapted to monitor at least one physiological variable o f a patient during an application of a positive gas pressure to an airway of the patient, to provide monitoring information representing the at least one physiological variable; and
a processing component including a deriving component in communication with the monitoring component to receive the monitoring information and, based on the monitoring information, to derive data representing a respiratory event characterized by vibration of body tissue along the airway;
said processing component further including a determining component coupled to receive said data and adapted to generate a control signal based on said data, said control signal including a modulated component that is substantially 180 degrees out of phase relative to said data and being applicable to control a gas delivery device to modulate said positive gas pressure in accordance with the modulated component of the control signal to counteract said vibration of body tissue, thereby tending to cancel the respiratory event.
The monitoring means may include means such as a plurality of sensors and/or transducers for acquiring and monitoring variables representing physiological states associated with the patient. The physiological variables can include respiratory effort, breathing airflow, oximetry and/or sound. To this end the monitoring means includes an air pressure wave or sound/acoustic vibration transducer to monitor breathing sound and/or air pressure waves associated with the patient""s respiratory function. The air or sound pressure wave transducer may include a sound microphone, air pressure sensor, air flow sensor or similar device. The air/sound pressure wave transducer may be located near the patient such as being incorporated in the nasal or nasal and oral mask used to deliver gas to the patient, or at any other location suitable for monitoring patient airflow and/or sound. Alternatively or additionally the apparatus may include other respiratory parameters input for the purpose of monitoring and detection of respiratory effort and/or respiratory disorders.
The or each sensor and/or transducer may generate an analog signal representative of variables being monitored. The monitoring means may include means for amplifying and/or performing analog processing on the analog signal. The latter may perform filtering and/or other wave shaping functions. The processed signal may be fed to an analog to digital converter to convert the or each analog signal to a corresponding digital signal. The or each digital signal may be fed to a digital processor such a microprocessor or microcomputer. The digital processor may include software for deriving from the or each digital signal data representing the patients respiratory state. The software may include means such as an algorithm for determining from the data a gas pressure value which substantially prevents a deterioration of the respiratory state. The algorithm may be adapted to generate a gas pressure signal which is substantially 180xc2x0 out of phase relative to the phase of the patient breathing air flow and/or sound together with an option of a further gas pressure signal which changes relatively slowly when compared to the out of phase signal. The latter may be used to control delivery of gas to the patient to cancel out or substantially compensate the effects of a breathing disorder. In the event that the breathing disorder is not substantially corrected the software may be adapted to activate delivery of a drug such as ventilum. This may circumvent what may otherwise be a fatal or severe asthma attack. The software may additionally be adapted to determine quantity requirements of the drug. The latter may be based on the patient""s history and the extent to which the disorder fails to respond to gas pressure treatment.